Needleless syringes perform injection without using an injection needle. They generally have a configuration in which pressure is applied to an injection liquid, which includes a medicine or the like, with the aid of a propellant, a pressurized gas, a spring, or the like. The pressure applied to the injection liquid is adjusted so as to deliver the injection liquid to a desired area inside a living body. Patent Document 1 discloses a configuration in which an injection liquid and a gas generating agent for applying pressure form one unit. The configuration also includes a lid that covers the unit. The unit is inserted into a syringe body before using the syringe. The inserted unit will be ready for injection when the lid is blocked. A new unit is loaded after the initial unit has been used. Thereafter, a subsequent injection procedure is performed.
Patent Document 2 discloses a configuration that includes an injection liquid holding portion and a pressurizing portion. The injection liquid holding portion retains an injection liquid. The pressurizing portion applies pressure to the injection liquid. The injection liquid holding portion is separated from the pressurizing portion. In this configuration, the injection liquid holding portion and a driving source of the pressurizing portion are replaced after the injection liquid is injected. Thereafter, a subsequent injection procedure is performed.
Patent Document 1: US Patent Specification No. 6258063
Patent Document 2: Japanese Translation of PCT Application No. 2003-535654
Patent Document 3: US Patent Application Publication No. 2003/0114789